Effect of subcutaneous carbon dioxide insufflation on arterial pCO2

Subcutaneous emphysema following laparoscopy could result in postoperative respiratory acidosis from prolonged CO2 absorption. We studied the magnitude and duration of alterations in PaCO2 coincident with direct CO2 insufflation into the subcutaneous fat of the anterior abdominal wall of 5 anesthetized juvenile pigs.

First, each pig was insufflated with 6 L of CO2 to produce moderate emphysema over the trunk. Following return to baseline PaCO2, each pig was re-insufflated with 12 L of CO2 to produce severe emphysema over lower limbs, neck, head, and trunk. Measurements of arterial blood gases were performed every 5 or 10 min. Minute ventilation was held constant to represent the worst case scenario.

From baseline PaCO2 of 41.8 +/- 2.3 mm Hg, PaCO2 peaked at 68.3 +/- 8.6 (P < 0.02) and 92.9 +/- 10.7 (P < 0.01) mm Hg for the 6- and 12-L volumes, respectively, 20 to 25 minutes following insufflation. From baseline arterial pH of 7.40 +/- 0.02, respective nadirs of pH were 7.21 +/- 0.06 (P < 0.02) and 7.08 +/- 0.05 (P < 0.01). PaCO2 and arterial pH took approximately 100 minutes to return to baseline after insufflation with both 6 and 12 L volumes.

When minute ventilation is fixed, subcutaneous CO2 insufflation causes increased PaCO2 and decreased pH that may persist for a prolonged period of time. Therefore, patients with subcutaneous emphysema after laparoscopy should be observed in postanesthetic recovery until PaCO2 and pH approach baseline.